Telephone-exchange system



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Patented June 23, 1925.

UNITED STATES PATENT OFFICE.

SAMUEL B. WILLIAldS, OF BROOKLYN, AND EDWARD E. HINRICHSEN, OF NEW YORK,N. Y., ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK,N. Y., A CORPORATION NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed April 30, 1923.

ratus for the establishment of connections.

The object of this invention is to enable an increase in the capacity ofgroups of lines or trunks, such as those leading to branch exchanges,without disturbing existing equipment and to otherwise improve theservice provided for said exchanges.

A feature of the invention relates to a system wherein, when aconnection is built up to a particular group of lines, the establishedconnection is partially released and is automatically reestablished to agiven one of the lines in the group.

Another feature relates to means, in a system having the lines of agroup appearing in one or more switches with provision for building aconnection through to one of said switches, whereby when the connectionis intended for said group it is temporarily released and automaticallyreestablished to an idle one of said lines in whatever switch it mayappear.

Other features and advantages contemplated by the invention will betaken up in detail hereinafter and pointed out in the appended claims.

Considering the drawing, Figs. 1 to 13, inclusive, taken in the orderillustrated in Fig. 14 disclose the details of a telephone systemincorporating the features of the present invention.

Fig. 1 illustrates a line switch of the coordinate type in which thesubscribers lines terminate and also two of a number of trunks outgoingto a district selector switch.

Fig. 2 shows the controlling elements associated with one of theoutgoing trunks.

Fig. 3 discloses a district selector switch of the coordinate type.

Fig. 4 illustrates a group selector switch of the coordinate type inwhich terminate Serial No. 635,421.

trunks incoming from the district selectors.

Fig. 5 shows one of a numberof coordinate connector switches forcompleting connections to called lines and P. B. X. trunks.

Fig. 6 represents a sender selector switch also of the coordinate type.

Figs. 7 and 8 illustrate one of a number of common register senders.

Fig. 9 shows at the left of the sheet a sender connector device forconnecting any of the senders with the common marker or selectioncontrolling device.

The remainder of Fig. 9 together with Fig. 10 disclose the common markerfor controlling the district switches.

Fig. 11 shows a sender connector device for connecting the line markerwith any of the several register senders. This figure also shows testingrelays for testing the trunks interconnecting the group selector andconnector switches together with certain control elements of the linemarker.

Fig. 12 discloses the remainder of the line marker.

Fig. 13 illustrates a second coordinate group selector switch similar tothe switch shown in Fig. 5 and belonging to the same group forestablishing connections to called lines and P. B. X. trunks.

General description of system and appalrows.

The line switch 100, selector switches 300 and 4100, connector switches500 and 1300 and the sender selector switch 600 employed in this systemare of the coordinate type such as shown and described in the patent toS. B. Williams, No. 1,517 .331, issued December 2, 1924. The subscriberslines enter the exchange and appear in the coordinate line switches 100in Vertical rows 110 and 111. each linehaving access to a group ofhorizontal links such as the groups represented by links 106 and 107 andlinks 108 and 109. Line 101, for instance, has access to the group oflinks containing the links 106 and 107. Each of the outgoing trunks 114,115, etc, occupies a full vertical row of contacts 112, 113 and leads tothe district switches.

Trunk 114 which is shown in full, appears in the district switch 300 inthe vertical row of contacts 308. Another trunk 115 is shown occupyingthe vertical row of contacts 309. The district selector switch 300 alsohas a plurality of groups of outgoing trunks appearing in rows 311, 312,313, etc. Each outgoing trunk is shown as hav ing an appearance before asingle horizontal link such as the links 303, 30 1, 305, 306 and 307.These trunks are multiplied to appear before corresponding horizontallinks in a number of district switches belonging to the same group.These other district switches also receive trunks incoming from otherline switches similar to the switch 100 serving other calling lines inthe exchange.

The subscribers lines are divided into a number of groups as calledlines known as terminal line groups. For convenience, there may be liveof these terminal line groups accommodating an exchange of 10,- 000lines in capacity, each such group serving 2,000 lines. As will beexplained hereinafter, each terminal line group is made up of a numberof group selectors and a number of connector switches. The trunksoutgoing from the district switches are, therefore, arranged to haveaccess to any of the five terminal line groups of switching apparatus.

The group of trunks appearing in the upper section 302 of the verticalrow 311 in the district switch 300 lead to the group selector switchesof a particular terminal line group. One of these trunks 350 is shownextending to the group selector switch e00. The group of trunksoccupying the lower section 301 of the same vertical row may lead to thegroup selectors of the same or of a different terminal line group asdesired. Other groups outgoing from the district switches aredistributed to other terl'ninal line groups. In addition to these groupsof trunks, the district switches may have access to trunks extending inother directions.

As above observed each terminal line group of switching apparatus isequipped with a plurality of group selectors and a plurality ofconnector switches. There will be as many connector switches as arenecessary to accommodate the 2,000 called subscribers lines togetherwith provision for as many P. B. X. trunks as may be required. Therewill be as many group selector switches as is necessary to extend thetrunks incoming from the district switches to the connectors. If thereare 2,000 lines in the group having directory numbers together with anumber of groups of P. B. X. trunks, these may be distributed in anysuit able manner among as many connector switches as the total number oflines and trunks utilize.

Each of the several district subscribers lines is provided with adirectory number and occupies a given position in one of the connectorswitches. Moreover, for each group of private branch exchange trunksthere is a single call-line which has a directory number identifying theP. B. X. and which is located in the connector switches along with theregular subscribers lines. The several trunks belonging to each privatebranch exchange group represented. by a call-mmiber line are, however,independent of directory numbers. In other words, for each P. B. X.call-line there may be as many trunks outgoing to the district P. B. X.represented as necessary and these may be located in one or in'a numberof connectorswitches in any arbitrary manner. In ort er to call a groupof P. B. X. trunks, the subscriber dials a number indentitying thatparticular P. B. X. group. The apparatus in the exchange establishes aconnection through the district switch into the group selector of theproper terminal line group and thence from the group selector to theparticular connector switch in which appears the correspondingcall-line. Immediately that the call-line is selected the connectionthrough the group selector and connector switches is released and isautomatically reestablished through the group selector and the properconnector to the first idle P. B. X. trunk of the required group. Ifthis first idle trunk is located in the same connector switch with thecall-line, then the connection is reestablished to the connector switchfirst used. However, the first idle trunk may appear in a ditterentconnector switch, in which case, the reestablished connection leads tosuch other connector switch and thence to the selected idle P. B. Xtrunk.

Considering the terminal line switching apparatus shown in the drawingthere are illustrated a number of direct subscribers lines 53st, 535,and 1322 appearing in the connector switches 500 and 1300. There is alsoillustrated a P. B. X. call-line 538 appearing in the switch 500 and anumber of P. B. X trunks 536, 537, 530, 1323 and 1324. connprising thegroup represented by the call-line 538. It will be noted that a portionof these P. B. X. trunks are located in the switch 500 with thecall-line 538, while the remainder of the trunks of this group aresituated in a second and difl'erentconnector switch 1300., It will beum'lerstood, as previously explained, that all of these trunks may belocated on a single connector switch or that they may be distributedamong still other connector switches in the group (not shown).

All numbered lines including both direct subscribers lines and P. B. X.call-lines appear in the connector switches in groups or vertical rowsaccording to their numbers. For instance, the vertical row of contacts532 in the connector switch 500 represents a group of ten lines. Onlythree of these lines are illustrated in the drawing, the two subscriberslines 534 and 535 and the. P. B. X. call-line 538. In the second switch1300 shown, the vertical row 1320 represents another group of tennumbered lines. In like manner, there will be as many of these verticalten-line groups in these and other connector switches as is neces saryto accommodate the full 2,000 numbered lines. In addition to thenumbered lines the P. B. X. groups also appear in vertical rows. Theparticular group shown occupies either all or a portion of the verticalrow 533 in the switch 500 and also either all or a portion of thevertical row 1321 in the switch 1300 according to the number of trunksnecessary for this particular group.

The connector switches are also provided with a number of groups ofhorizontal links, each group having access to all numbered lines of aparticular units designation together with P. B. X. trunks. For example,the group of links comprising the links 501 and 502 have access to thecall-line 538 in the row 532, to the trunk 536 in the row 533 and alsoto other lines or trunks in other rows (not shown). The horizontal testlink 503 is associated with this group of horizontal links and servesfor test purposes as hereinafter described. For each of the remainingnine units designations, there is a group of these horizontal linkshaving access to lines andtrunks. Two of these groups, one including thehorizontal links 504, 505 and 506 and the other includii'ig links 507,508 and 509, are illustrated. In a similar manner the switch 1300 has anumber of groups of horizontal links of which the links 1301 to 1306 area portion.

The district marker shown in Figs. 9 and 10 includes two sets of testingrelays 1000 and 1003. The set 1000 serves to test the horizontal linksof the section 302 in any district selector switch with which it isassociated and also to test the outgoing trunks which have access tothese links. The connecting device 1002 which comprises a number ofmulti-contact relays 1015, 1016, etc., serves to connect the set ofrelays 1000 with the proper group of outgoing trunks, the multi-contactrelays each being individual to a different group. Likewise, the otherset of test relays 1003 serves to test the setof horizontal links 301 inall switches and the outgoing trunks to which these links have access.Also a connecting device 1001 consisting of multi-contact relays 1022,1023, 1019, 1020, 1025 and 1026 serves to connect the marker testingrelays with the individual switches. Relays 1023. 1020 and 1026, forinstance, are individual to the particular switch 300 shown in thedrawing.

The line marker shown in Figs. 11 and 12 includes a plurality ofregisters 1200, 1201. and 1202 which receive numerical records from thecontrolling sender. It also includes the multi-contact relay translatingdevice 1204 which is operated according to the settings of the registersto select the vertical operating magnets 515, 1308, etc.,

individual to the different vertical rows of numerical lines in theconnector switches. Moreover, the line marker includes a multicontactrelay translating device 1203 which serves to associate the register1201 with the connecting devices 510 and 1316 individual to theconnector switches 500 and 1300, respectively. The device 510 consistingof relays 511, 512, 513, etc., serves to associate certain test relaysin the marker with the horizontal links of the group having access tothe called lines of the desired units designation in the connectorswitch 500. The device 1316 similarly comprising a number ofmulti-contact relays 1317, 1318, etc., serves to connect the sametesting relays in the marker with the horizontal links of the grouphaving access to the called lines of the desired units designation inthe connector switch 1300. In Fig. 11 the set of testing relays of themarker are associable through the multi-contact relay connecting devices4-01 and 102 with the groups of trunks outgoing from the selector switchand other switches and with the horizon tal links of these groupselectors.

Detailed description of estabiislwnent 0/" a connection.

inner contact of cut-off relay 120, conductor 1 104:, through thesubstation loop, conductor 103 to ground through the outer contact ofrelay 120. Relay 121 operates and a circuit is closed from batterythrough the winding of relay 129, right back contact Of 1 relay 128,left contact of relay 121, conductor 156 to ground.

Relays 128, 129 and 130 enclosed within the broken rectangle pertain tothe vertical group of lines in the row of the switch 100. These relaysare brought into action whenever one of the lines of the correspondinggroup initiates a call.

Relay 129 completes a circuit from battery through the winding of relay131, inner front contact of relay 129 to the grounded conductor 156.Relay 129 also closes a circuit from battery through the left handwinding of relay 130. outer "front contact of relay 129, left backcontact of relay 135, outer right contact of relay 137, conductors 158and 156 to ground. Relay 130 operates and closes a circuit for relay128. Relay 128 looks through its left contact and the contacts of relays1.31 and 132 to ground. Relay 130, in operating, completes a circuitfrom battery through its right hand winding and inner right contact,winding of relay 135, outer right contact of relay 137, conductor 158 toground. Relay 135 operates and closes a circuit from battery through thewinding of slow-to-release relay 136, inner right contact of relay 135,inner right back contact of relay 137, conductor 158 to ground. Relay136 closes a substitute holding circuit for relays 130 and 135.

With relay 135 operated, a circuit is closed from battery through thewinding of the vertical operating magnet 116, outer right front contactof relay 130. left front contact of relay 1355, contact of relay 136,conductor 158 to ground. The magnet 116 operates and prepares thecontacts in the vertical row .110. Magnet 116 also closes a circuit fromground through its contact, conductor 159, innor contact of relay 131,outer left contact of relay 130, right contact of relay 121, left handwinding of the horizontal group relay 122 to battery. Relay 122 is agroup relay individual to the group of horizontal links including thelinks 106 and 107. Similarly, relay 123 is a group relay individual tothe other group of horizontal links illustrated.

Relay 122 operates and closes a circuit from battery through its righthand winding and right contact. right back contact of re lay 123,winding of relay 13 1, conductor 159 to ground. Relay 134 operates inthis circuit. Another circuit is closed from battery through the windingof the vertical operating magnet 118, brush 1 141 of allotter switch143. contact of slow release relay 139, left contact of relay 137, outerright contact of relay 135, conductor 158 to ground. It is assumed thatthe first one of the outgoing trunks 114 is idle and that the allotterswitch 143 is standing in a. position to allot this trunk as shown inthe drawing. The allotter switch 143 has a position for each of theseveral trunks which lead out of the line switch to the succeedingdistrict selectors. Consequently. the vertical magnet 118 relative tothe idle trunk 1141 operates and prepares the contacts in the verticalrow 112. hilagnet 118. in operating. completes a circuit from batterythrough its winding and inner contact. conductor 160. winding of relay137, outer right contact of relay 135, conductor 158 to ground. Relay137, however. being shunted by the circuit above traced does not operatethis time. Magnet 118. furthermore, closes a circuit from ground throughits outer contact, conductor 151,

winding of trunk relay 14:6 to battery. l l ith relay 1416 operated acircuit is completed from battery through the winding of relay 139,winding and contact of stepping magnet 13S, brush 1&5, contact of relay14:6 to ground over conductor 151. The magnet 138 operates, interruptsits own circuit and advances the brushes 14A and 1415 to the next set ofterminals. If the following trunk is idle then the allotter switch comesto rest,

but if it is busy, the switch continues until an idle trunk is found.hen the switch leaves the position shown it opens the shunt around relay137 and this relay operates in series with magnet 118. Relay 137 opensthe circuit of relay 136 which commences to deenergize. Relay 136 beingslow, holds its armatures for an interval after the release of relay 137which is sufficient for certain operations to take place.

During the interval mentioned a circuit is closed from ground overconductor 158, inner right front contact of relay 137, outer contact ofrelay 134, left back contact of relay 123, left front contact of relay122, back contact of relay 127, assuming the first link 107' is idle,winding of magnet to battery. Magnet 125 operates and effectsaconnection between the link 107 and the incoming line and also betweenthe link and the outgoing trunk 11 1. Immediately that this connectionis established, a circuit is closed from battery through the winding ofmagnet 125, winding of relay 127, cont-acts of the switch 100, over thesleeve conductor to ground at the outer contact of magnet 118. Theswitch is temporarily held by means of this circuit but relay 127 beingshunted does not operate at this time. An other circuit is closed frombattery through the winding of cut-01f relay 120 over the sleeveconductor to ground at the contact of magnet 118. Relay 120 opens thecircuit of relay 121, which in turn, opens the original energizingcircuit of relay 129.

Should another line in the same vertical group attempt simultaneously tomake a call while a subscriber in a succeeding vertical group iscalling, his attempt to make such a call will be unsuccessful. When theline relay 121 releases following the opening of its circuit by relay120, it opens the holding circuit of relay 131, but since the secondsubscriber in the same group is calling relay 131 is held energized overa parallel circuit through the left contact of the line relay similar torelay 121. Relay 131 in remaining energized preserves the lockingcircuit of relay 12 which prevents the reenergization of relay 129. Asecond subscriber in the first group Who has removed his receiver whilethe line relay of the first calling subscriber is energized, therefore,cannot succeed in making a call until a simultaneous call in subsequentgroups have been handled or until a call has been made in each of saidsucceeding groups. In this latter event a series circuit is closed forrelay 132 through the back contacts of all relays similar to relay 129and relay 132 operates to unlock relay 128.

At the instant relay 146 energizes, the ground potential on conductor151 is extended through the contact of this relay over conductor 150,through the back contact of relay 204, conductor 206, thence through thewinding of relay 613. Relay 613 operates and locks through its windingand inner left contact, conductor 207, outer left back contact of relay201 to ground. Relay 613 completes a circuit from ground through itsouter right contact, conductor 209, winding of slow-to-release relay 204to battery. Relay 204 operates and applies holding ground to theconductor 150, whereby magnet 125 and relays 120 and 146 are heldenergized when magnet 118 becomes deenergized. Relay 613 operatessimilarly to the relay 120 of the line switch and brings the grouprelays 614. 615 and 616 and the control relays 619, 620, 621, 617, 622and 623 into play to cause the extension of a connection through thesender selector switch 600 to the allotted idle register sender.

With relays 616 and 617 operated a circuit is closed from batterythrough the winding of vertical magnet 629, contacts of relays 616 and617, outer right contact of relay 623 to ground. Magnet 629 operates andbrings about the energization of relay 612, which in turn, locks in acircuit including the re lay 621. Relay 617 also closes a circuit frombattery through the winding of vertical magnet 631, brush 627 ofallotter 626, contact of slow relay 625, left contact of relay 623,contact of relay 617 to ground. The magnet 631 operates and closes alocking circuit through its winding and contact and the winding of relay623, the latter relay, however, remaining deenergized due to the shuntaround its winding. Magnet 631 also closes a circuit from ground throughits outer contact, conductor 638, through the brush 628, contact andwinding of magnet 624, winding of slow relay 625 to battery. Magnet 624steps the switch 626 forward to the set of terminals representing thenext idle sender and in so doing removes the shunt from the winding ofrelay 623. Re-

lay 623 opens the circuit of slow-to-release relay 622 which commencesto deenergize. During the interval that relay 622 is deenergizing'acircuit is closed from ground through the inner right front contact ofrelay 623. rightcontact of relay 621, left front contact of relay 612,front contact of relay 611. assuming the link 608 to be busy, hackcontact of relay 609, winding of the iorizontal magnet 610 to battery.Magnet 4 610 operates the switch and connects the incoming trunkconductors through the link 607 to the group of conductors 632 leadingto the selected idle sender.

Immediately that the connection is es tablished a circuit is closed frombattery through the winding of relay 201, conductor 210, contacts ofswitch 600, conductor 638 to ground at the contact of magnet 631. Relay201 operates and opens the circuit of relay 613 which causes thedeenergization of relays 612 and 619 provided no other sender is beingsought through the same vertical group in the switch 600. Relay 201 alsocloses a holding circuit for the relay 204 which maintains a holdingground potential on the conductor 150. Furthermore, relay 201 connectsthe tip and ring conductors of the trunk through the sender selectorswitch to the impulse relay 700 and balancing coil 701 of the sender.This results in the closure of a circuit from battery through theresistance 718, winding of relay 700, outer left contact of relay 703,conductor 640, through contacts of the switch 600, conductor 641, outerright contact of relay 201, conduct-or 149, thence through the lineswitch 100 and the subscribers substation loop and returning over theother side of the line to conductor 148 to the inner right contact ofrelay 201, conductor 642, through the switch 600, conductor 643, innerleft contact of relay 703, right hand winding of the balancing coil 701to ground. Relay 700 operates and closes a circuit for slow-to-releaserelay 702. Relay 702 places ground on the holding conductor 720. Thisground potential is transmitted by way of conductor 638 and results in aholding circuit for the magnet 610 and relays 609 and 201 insubstitution of the circuit temporarily maintained by the vertical.operating magnet 631.

Following the series of operations just related slow relays 136 and 622become deenergized. Relay 136 opens the circuits of relays 130 and 135.Relay 130 opens the circuit of magnet 116 and relay 135 opens theholding circuit of magnet 119 and relay 137. Magnet 116 causes therelease of relays 134 and 122. YVith the vertical magnets deenergizedthe connection is now held through the line switch 100 due to themaintained energization of magnet 125 which, as above mentioned, is heldin a circuit closed to ground over the sleeve conductor 150. Relay 127now operates in series with magnet 125 and extends the horizontal startcircuit to the next link. Relay 622, in releasing, similarly bringsabout a release of the corresponding elements in the sender selectorswitch 600 and the connection through this switch is now held by themagnet 610, the circuit of which is controlled by the slow relay 702 inthe sender. Relay 609 now operates in series with magnet 610.

llU

or u- The apparatus is now in condition for receiving the first seriesof impulses. The calling subscriber, consequently, manipulates hisimpulse transmitter 163 to send a single impulse representing the firstdigit of the wanted number. At the time relay 702 operates it closes acircuit from battery through the winding of slow release relay 706, leftback contact of relay 704, left back contact of relay 705, conductor720, to ground at the left contact of relay 702. Relay 702 also closes acircuit from battery through the resistance 739, left hand winding ofrelay 707 to ground at the right contact of relay 702. Relay 707,however, does not oper ate since its winding is shunted by the followingpath: battery, through the resistance 739, contact of relay 700 toground at the right contact of relay 702.

In response to the first opening of the line by the calling subscriber,relay 700 rcleases and opens the shunt aroun: the winding of relay 707and this latter relay operates. Relay 707 closes a circuit from batterythrough the winding of relay st, outer left contact of relay 707 to thegrounded conductor 720. Relay 70et operates and locks in a circuitthrough its left front contact, left contact of relay 705 to ground onconductor 720. Relay 70% opens the original circuit of relay 706, butthis latter relay remains energized in a circuit traceable through theouter right front contact of relay 707 to the grounded conductor 720..K-elay 707 closes a circuit through the left hand winding of relay 708and relay 708 operates and closes a circuit from battery through itsright hand winding and inner right contact to the grounded conductor720.

Relay 708, in operating completes a circuit from battery through itsleft hand winding and left contact, conductor 72%, outer right backcontacts of counting relays 715, 714L, 713 and 712 in series, winding ofrelay 712, outer left back contact of relay 713, conductors 725 and 726,outer right contact of relay 705, left front contact of relay 704i, leftcontact of relay 705 to the grounded conductor 720. So long as relay 707remains operated relay 712 is shunted and does not receive suflicientcurrent in the circuit traced to energize. At the end of the impulserelay 700 operates and shunts relay 707 and this relay releases, openingthe original circuit through the left hand winding of relay 708. Relay712 now operates in series with the left hand winding of relay 708.Relay 712 locks in a circuit from battery over conductor 727, innerright contact and winding of relay 712, outer left back contact of relay713 to ground over conductor 7 It should be noted at this point that thearmatures of the counting relay 712, which is also true of the remainingcounting relays, are so arranged that the inner right contact is closedslightly in advance of the opening of the outer right back contacts. 3ythis arrangement the locking of the relay is certain to occur before theenergizing circuit is opened.

Immediately that the relay 712 opens its back contact the circuitthrough the left hand winding of relay 708 is opened. Relay 708 is wounddifferentially and when the left hand winding is opened, the effect ofthe right hand winding is to cause a quick release.

After the usual interval has elapsed following this impulse,slow-to-release relay 706 becomes deenergized and a circuit is completedfrom ground over conductor 720, contact of relay 706, right contact ofrelay 70st, inner right contact of relay 705, conductor 722, right backcontact of relay 808, winding of relay 807 to battery. Relay 807operates and closes a circuit from battery through its winding and innerupper cont-act, thence over conductor 830 winding of relay 705, throughcontacts of relays 70 i, and 706 to ground. Relay 705, however, beingshunted by the above circuit does not operate at this time. Relay 807serves to connect the counting relays to the register relays of theregister 800. With relay 807 operated and relay 712 energized a circuitis closed from the grounded conductor 725, outer left front contact ofrelay 712, conductor 728, outer right back contact of relay717,-conductor 729, conductor 831, contact of relay 807, thence inparallel one branch leading through the winding of relay 804 and thewinding of relay 832 to battery and the other branch leading through thewinding of relay 823 to battery. Relays 804, 832 and 823 operate andlock through the inner left front contact of relay 804, conductor 825 tothe grounded conductor 720. Relay closes an obvious circuit for relay808 which operates and locks to the grounded conductor 825. Relay 808opens the shunt around the winding of relay 705, which energizes inseries with relay 807. Relay 705 opens the circuit of relay 704, whichin turn, opens the circuits of relays 705 and 807. Relay 807 disconnectsthe counting relay from the register 800. Vith relays 7 04 and 705deenergized relay 706 again operates in the cirucit abo e traced. Relay705 also releases relay 712.

The subscriber operates his dial to trans mit the second seriesconsisting of two inipulses and in the manner already fully explainedrelays 712 and 713 are operated. Relay 713, in operating, opens theholding circuit of relay 712 which thereupon releases. After the properinterval has elapsed follow ing the series. slow relay 700 releases anda circuit is closed from ground. over conductor 722 as above traced,through the right front: contact of relay 808, right back contact ofrelay 812, winding of relay 811 to battery. Relay 811 operates, connectsthe counting relays to the second register 801 and closes a lockingcircuit through its winding and inner upper contact, over conductor 830as previously traced, through the winding of relay 705. Relay 705 beingshunted does not operate at this time.

Since the counting relay 713 is operated a circuit is traceable from thegrounded conductor 725, through the outer left front contact of relay713, conductor 730, conductor 837, through contact of relay 811 windingof register relay 810 to battery. Relay 810 locks through its inner leftcontact to the grounded conductor 825. Relay 810 at its outer leftcontact closes a circuit for relay 812 which operates and locks to theconductor 825. Relay 812 opens the shunt around relay 7 05 whichoperates and in the manner explained brings about the release of relay704, relay 718 and relay 811 and also releases itself.

The subscriber next transmits the third series consisting of threeimpulses. In response to this series relays 712, 713 and. 714 areoperated and relays 712 and 713 successively release. After an intervalrelay 706 releases and closes a circuit as traced over conductor 722,through the right front contacts of relays 808 and 812, right backcontact of relay 816, winding of relay 815 to battery. Relay 815operates, connects the counting relays to the register 802 and closes alocking circuit for itself over conductor 880 through the winding ofrelay 705.

With relay 815 operated and the counting relay 714 energized, circuitsare closed from ground over conductor 7 25, through the left frontcontacts of relay 714, conductors 729 and 780, thence over conductors881 and 887, through contacts of relay 815, windings of relays 818 and814 to battery. Relays 813 and 814 lock through their inner leftcontacts to the grounded conductors 825. These relays also close acircuit for the relay 816 which operates and locks through its leftcontact to the conductor 825. Relay 816 opens the shunt around relay705, which in turn. operates in series with relay 815. In a similarmanner to that already explained relay 705 brings about its own releaseand the release of relays 704 and 815.

The subscriber now transmits the final series consisting of fourimpulses. In response to this series counting relays 712, 713, 71.4 and715 are operated in succession and relays 712, 713 and 714 are releasedin succession. After an interval relay 706 releases and a circuit isclosed by way of conductor 722, through the right front con tacts ofrelays 808, 812 and 816, right contactof relay 820, winding of relay 819to battery. Relay 819 connects the counting relays to the register 803and closes a. locking circuit for itself over conductor 830, through thewinding of relay 705. Vith relay 819 operated and relay 715 operated acircuit may be traced from ground over con.-

ductor 725. outer left back contact of relay 712, inner left contact ofrelay 715, conductor 731, conductor 838, through contact of relay 819,relay 833 to battery. Relay 833 locks through its inner left contact tothe grounded conductor 825. Relay 833 closes a circuit for relay 820which looks through its inner left contact to conductor 825. Relay 820opens the shunt around relay 705 which brings about its own release andthe release of relays 704 and 819.

As soon as the thousand digit is recorded on the register 800, thesender is connected to the district marker in order that the record maybe transferred thereto for detern'iining the group selective operationof the district switch 300. hen relay 808 operates a circuit isestablished from the grounded conductor 825, through the outer leftcontact of relay 808, conductor 839. winding of relay 709 to battery.Relay 709 operates and locks through its outer contact to the groundedconductor 720. Relay 709 closes a circuit from the grounded conductor720, through the outer left contact of relay 711, inner contact of relay709, conductor 7 32, winding of relay 904 to battery. Relay 904 closes acircuit from ground through its right contact, right contact of relay907. winding of relay 908 to battery. Belay 908 operates and locksthrough its inner contact, middle back contact of relay 909, conductor914, contact of slow relay 912 to ground. Relay 908 closes a circuitfrom battery through the right winding of relay 903, left contact ofrelay 904, left back contact of relay 906, outer contact: of relay 908,middle back contact of relay 909, conductor 914 to ground. Relay 903closes a circuit for relay 907. Relay 907, in turn, closes a circuitfrom battery through the left winding and contact of relay 903, leftback contact of relay 905, left contact of relay 907, winding of relay909 to ground over conductor 914. Relay 903 is locked and relay 909operates in this circuit. Relay 908 now becomes released. Relay 909causes a. circuit to be closed for the multi-contact relay 901, which isindividual to the particular sender shown and serves to connect thatsender with the district marker. Another multi-contact relay 902 isindividual to another sender and serves for a similar purpose. Thecircuit of relay 901 leads from battery through the winding thereof,inner right contact of relay 903, inner contact of relay 909 to thegrounded conductor 914. Relay 901, in operating, closes a circuit fromground through its contact, outermost contact of relay 909, inner leftback contact of relay 911, Winding of relay 910

